The longest of the classes is the Valiant-class coming in at 1,518 metres (4,980 ft),[4] followed by the Autumn-class at 1,425 metres (4,680 ft),[5] then the Marathon-class at 1,192 metres (3,910 ft),[4] and finally, the Halcyon-class, the smallest, at 1,170 metres (3,800 ft).[6]

Mass wise, the Halcyon was said to be one-third the tonnage of the Marathon.[3]